This invention relates to communications system controlling devices and in particular a controlling device for a single channel radio communications system. Reference is made to two additional co-pending applications, Ser. Nos. 564,950 and 564,855, filed on the same date as the present invention and containing related subject matter.
Direct mobile-to-mobile radio communication is limited in range by low antenna heights and relatively low power transmitters. In order to overcome these limitations and cover larger geographical areas, the concept of a single channel "community repeater" has developed whereby a receiver is coupled to a higher power transmitter at a location of favorable radio propagation. Signals from a mobile radio transmitter are received by the community repeater receiver and routed to the community repeater transmitter for rebroadcast to receiving mobiles. Many diverse groups of mobile users in the same community can utilize the same "repeater" by transmitting and receiving on the appropriate frequencies. Generally, the type of communication on a community repeater is a "push-to-talk, release-to-listen" message transmission of short duration between one mobile user and a kindred group of at least one other mobile user.
Crowded conditions can develop on the single communications channel as many different groups consisting of many mobile users attempt to use the channel. Common courtesy is often abandoned as mobile users transmit simultaneously in an effort to capture the channel and communicate their message. Mobile users who listen for a message directed to them or their group are exposed a cacophony of messages which are not of interest and may obscure the desired message.
To improve this situation, a number of developments, which are now well known, have been made. Special coding schemes utilizing continuous subaudible signals or precursor signals are transmitted by a mobile to activate a controller at the community repeater enabling the retransmission function. These signals also activate, via the repeater, other mobiles in a common communications grouping known as a fleet. Directed calls of this sort reduce annoyance to the mobile user for he no longer has to listen to every message on the channel, but they add to his operating burden as he must monitor the channel before transmitting. Also, even with the code activated repeater controller, access to the channel remains uncontrolled and contentious.
The repeater controller, in the well known coordinated multi-channel radio systems, utilizes computer mediated allocation of a plurality of radio channels to a large number of mobile transceivers. Service requests from the mobiles are transmitted to the repeater controller on signalling channels designated to receive the request. Permission to transmit and specification of which channel to use are returned to the mobiles on the signalling channels. The coordination and balance of requests for service and message transmission, which is necessary on a single channel, is neither necessary nor addressed in the multi-channel protocol. Consequently, although coordinated multi-channel controllers are effective in reducing contention, the multi-channel protocol used by these controllers is unsuitable for a single channel controller.
In addition to radio systems, the expanding field of multi-terminal processing has also generated an extensive need for sharing a scarce resource, i.e. a computer processor, among a large number of users. Time-sharing systems, which have been developed as a result of this need, typically place both request for service and message in a storage queue where they are subsequently analyzed by an allocation mechanism for eventual assignment to the computer processor. Unlike the present invention, which must coordinate the requesting process with real time message transmission on the single communications channel, the scarce computer processor resource is aloof from the requesting process and operates on the message in other than real time.
The central controller disclosed herein operates in the Queued Community Repeater (QCR) Communication System disclosed in co-pending application Ser. No. 564,950. The present invention, for the first time, affords real time community repeater users relief from the aggravations of a crowded communications channel. Users' satisfaction improves once contention for this channel is handled automatically and once necessary user manipulations of the mechanics involved in obtaining service on the channel are reduced. In addition, channel efficiency is increased as more mobiles can be accommodated on the single communications channel due to the automated control exercised.